This circuit was found in a 90s Popular Electronics. It is used for the acoustic transmitters of 40 kHz, as several found in this section. Transistors support current equivalents.
A first circuit that uses a phototransistor as a detector and is suitable for covering short...
We found this circuit in recent English documentation. The circuit uses CMOS technology and can be...
We found this circuit in an old Mullard (Philips) documentation on the 555 and 556 integrated circuit...